If you wouldn't pour Drano on your head, don't use any hair-relaxing product that contains lye, otherwise known as sodium hydroxide. It's the same powerful alkaline chemical used in drain cleaners to dissolve clumps of hair and other gunk clogging your pipes. Even in lower doses, lye can [dramatically] weaken your hair follicles, not to mention irritate your scalp; dry, crack and burn your skin; cause irreversible baldness; and make you go blind. Many "no lye" formulas have [now] been introduced, but they aren't necessarily better--the calcium hydroxide and guanidine carbonoate replacing it are still quite caustic and likely to cause skin irritation and hair breakage.
I wanted to make sure I mention that sodium hydroxide in higher concentrations, along with other chemicals used in relaxing the hair, is what she's focusing on. There are many other products out there that use sodium hydroxide to normalize the pH levels of products(likely less than 1% of the whole formula) and it's also used in hot-processed soaps. But with the latter, shampoo/body bar users need to be aware of how the lye in these bars can potentially RAISE the pH, raising/roughening the cuticles. Factor in hard water and mineral deposits FROM that water, and you can experience tangling and other issues.
I know, I know. Always something, right? Just some more food for thought. Eat it up!